Research On Photometric Characteristics Of Crystalline Silicon Cell Laminated With Opticalfunctional Textured Film

At present,crystalline silicon cells account for about 90% of the total global photovoltaic(PV)production.In recent decades,their conversion efficiency has continuously improved and gradually approached the limited theoretical efficiency(33.7%).The reported industrial conversion efficiency of crystalline silicon cells is about 23%.The key to improve the PV conversion efficiency of crystalline silicon cells is how to reduce the surface reflection loss and enhance the PV effect.Nowadays,the optical absorbance of crystalline silicon cells is improved mainly by the preparation of optical functional texture or laminating optical functional textured films on the surface of cells.Although the preparation of optical functional texture on the surface of crystalline silicon directly can help increase the absorbance of the cell,it will cause new surface defects and then reduces the PV effect.In addition,the gate electrode on the surface of crystalline silicon cell will cause shading loss and limit the improvement of light absorption.On the surface of the smooth crystalline silicon cell with fewer defects,the laminated light trapping textured film can effectively improve its absorbance.However,the existing optical functional texture film surface microstructures are all nanoscale,which is not conducive to rapid promotion because the manufacturing process is complex.Based on this background,a light trapping textured film with a pyramid array on the surface is laminated on a smooth crystalline silicon cell with high PV effect,which can improve the conversion efficiency of the cells.The optical functional textured film laminated on the surface of cells is prepared by hot embossing technology.This paper mainly conducts research from the following aspects:(1)Based on a comprehensive analysis of the adverse effects of the existing preparation methods of the optical functional texture on the photoelectric characteristics of crystalline silicon cells,a new type of laminated structure cell was proposed,which was laminated light trapping textured film on the surface of a crystalline silicon cell.Based on geometric optics theory,the light propagation process and the light trapping mechanism on the inner and outer surface of the light trapping textured film were analyzed.The antireflection characteristics of textured surface crystalline silicon cell and laminated structure cell were studied.(2)The effects of geometric parameters on the photometric characteristics of the light trapping units of the light trapping textured film were analyzed.Mathematical calculation model of the light trapping unit an outer surface reflection losses and the inner surface reflection loss was established.The light tracing calculation was used to optimize the geometric parameters of the light trapping unit on the surface of the laminated structure cell.To evaluate the inhibition effect of the retroreflective function of the inner surface of the light trapping film on the shading loss of the gate electrode on the crystalline silicon cell,a laminated structure cell model with the best anti-reflection effect was obtained.The effects of passivation film,refractive index of light trapping textured film and incident angle of light on the photometric characteristics of laminated cell are analyzed theoretically.A new structure of the laminated cell module was proposed and its photometric characteristics were studied.(3)Chemical etching was used to prepare smooth and textured surface crystalline silicon cells.According to the polymer material characteristics and light tracing calculation results,light trapping films were prepared experimentally and the surface quality of the sides of the pyramid was tested.The laminated technology of light trapping film and smooth surface crystalline silicon cell was studied and designed.In order to accurately assess the reflection loss of different cells within the visible light wavelength,a weighted reflectance calculation method at full wavelength was proposed in combination with the absorption characteristics of crystalline silicon material and the energy distribution characteristics in the visible spectrum.Finally,the photoelectric characteristics of the smooth surface crystalline silicon cell,the textured surface crystalline silicon cell,and the laminated cell were analyzed.The comprehensive evaluation of the photoelectric characteristics of the laminated structure cell was obtained.The research indicates that most of the incident light will enter the film after being refracted multiple times on the surface of the light trapping film.The light trapping textured film can significantly reduce the reflection loss of the smooth crystalline silicon cell.The best geometric parameter of the light trapping unit on the surface of the laminated structure cell calculated by the light trace is the base angle β = 67 °.Experimental analysis shows that the final measured weighted reflectivity of laminated cell is 6.57%,which is 8.57% and 1.65% lower than that of smooth and textured surface crystalline silicon cell,respectively.The PV conversion efficiency of the laminated cells is 20.34%,which is 2.33% and 1.18% higher than that of the smooth and textured surface crystal silicon cell,respectively.